How to identify an unknown radio tuner

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Radio frequency tuners can be found in a lot of devices, starting with TV sets, set top boxes and PC tuner cards. A tuner is a device that takes a ”chunk” of a frequency carrier of a bandwidth, amplifies it and then shifts it (usually by down-converting) into a fixed frequency that will be fed into a demodulator device. Tuners are difficult to build and a DIY tuner will never have the performance of one from a radio receiving device. The RF signal enters a baseband amplifier. Further, this signal is mixed with a local oscillator with variable frequency. The result exits the tuner as Intermediate Frequency (IF). Sometimes the tuner also contains a filter at the IF output. These functional blocks can be integrated into a superheterodyne receiver with ease (just add a detector). So, what can you do with a tuner? Keep reading.

How to identify an unknown radio tuner

Gray-Hoverman, the wideband TV antenna

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In the past, air TV channels were broadcast on frequencies ranging from 170 MHz to 860 MHz. The VHF-Hi band covers 175 to 230 MHz, while UHF covers 470 to 860 MHz. This is a large interval, covering two bands and it is difficult to receive with a single antenna. But, nowadays the UHF band for TV broadcasts is getting smaller. Frequencies starting from 600 MHz are being repacked for mobile networks.

The Gray-Hoverman antenna has been designed by Doyt R. Hoverman and it was patented in the sixties. It only covered the lower part of UHF, from 470 to 720 MHz (21 - 52 channels). If that could have been a problem, it's not anymore. The average gain in this frequency range is 13 dBi with reflector and 9.2 dBi without it. With some additional elements, this antenna can also receive the upper part of VHF from 170 to 230 MHz, with an average gain of 8.1 dBi with reflector and 6 dBi without it. The overall gain is not too much but, since it is easy to build and wideband it's worth a try. The original design has been republished and distributed according to the GNU GPL version 3 license.

Gray-Hoverman with NARODs, the wideband TV antenna